The present invention relates to a hair dye composition that provides high dyeing power, can strongly impart the hair with an extremely vivid purple color or an extremely vivid violet color has less color fade over time and undergoes only a small change in the color tone even after storage.
Hair dyes can be classified by the dye to be used or by whether they have any bleaching action on melanin. Typical examples include a two-part permanent hair dye composed of a first part containing an alkali agent, an oxidation dye and optionally a direct dye such as a nitro dye and a second part containing an oxidizing agent; and a one-part semi-permanent hair dye containing an organic acid or an alkali agent, and a direct dye such as acid dye, basic dye or nitro dye.
The above-described permanent hair dye is however accompanied with the drawbacks that the color tone imparted by an oxidation dye is not so vivid and that the color of the hair dyed with a vivid-color producing nitro dye ordinarily employed as a direct dye markedly fades over time and becomes dull quickly even if the color tone immediately after dyeing is very vivid (Japanese Laid-Open Publication No. Hei 6-271435).
Recently, hair dyes containing as a direct dye a so-called cationic dye having a cation group contained in their conjugate system have been reported (Japanese Laid-Open Publication No. Hei 8-507545, 8-501322(which will hereinafter be called xe2x80x9cJP1996501322xe2x80x9d) or 10-502946, or Japanese Laid-Open Publication No. Hei 10-194942, or International Patent Application Laid-Open No. 99/07334(which will hereinafter be called xe2x80x9cWO99/07334xe2x80x9d). They have been found to involve drawbacks that intended dyeing effects are not available owing to decomposition of them caused by mixing, upon hair dyeing, with hydrogen peroxide ordinarily employed as an oxidizing agent; and that they are unstable to an alkali agent or a reducing agent essentially contained in a permanent hair dye.
An object of the present invention is to provide a hair dye composition which can strongly impart the hair with a vivid purple or violet color range without decomposing the dye upon hair dyeing, and has excellent light resistance, washing resistance, perspiration resistance, friction resistance and heat resistance, and show high storage stability within a pH range of from 2 to 11 which is a pH range ordinarily employed for a hair dye, is stable against any one of an alkali agent, an oxidizing agent and a reducing agent, has high hair dyeing power, has less color fade over time.
The present inventor has found that when the below-described compound which is known as a cyanine photosensitizing dye for photosensitive materials laser filters, laser marking or optical data storage and is typified by S361(commercial name) provided by FEW chemicals GmbH, the resulting dye composition can strongly impart the hair with a vivid purple color without decomposing the dye upon hair dyeing, exhibits excellent light resistance, washing resistance, perspiration resistance, friction resistance and heat resistance, and undergoes a very small change in the color tone after storage compared with that immediately after preparation.
In one aspect of the present invention, there is thus provided a hair dye composition comprising, as a direct dye, a compound represented by the following formula (1) or (2): 
[wherein, R1, R2, R3, R4, R5 and R6 each independently represents a C1-6 alkyl group which may have a substituent; R7 and R8 each independently represents a hydrogen atom, a hydroxy group, a C1-6 alkyl group which may be substituted by a hydroxy group, a C1-6 alkoxy group, an amino group which may be substituted with one or two C1-6 alkyl groups which may be substituted by a hydroxy group; R9 represents a hydrogen atom or a C1-6 alkyl group; and Xxe2x88x92 represents an anion].
In another aspect of the present invention, there is also provided a hair dyeing method comprising applying the above-described hair dye composition to the hair.